Hitherto, in the multicolor liquid crystal display device, as a method for providing the color filters, it is well known to use a method comprising forming gelatin layers above or beneath the electrodes on an inner surface of the substrate and dyeing the gelatin layers to form the color filters. However, in the case of this method, there has been a problem in that both the water resistance and the heat resistance are low. In addition, in order to perform a multicolor patterning, a resist layer for anti-dyeing must be formed for each color by the use of a photolithographic process and removed subsequently, with the consequence that it must employ an increased number of process steps, thereby increasing the price of the product.
In view of the above, the inventors of the present invention had got an idea of forming the color filters by the use of a printing process and had completed the following invention with a view to solving the above discussed problems, which was applied for patent in Japan (Japanese Patent Application No. 58-119281). Namely, this invention is a color filter for a liquid crystal display device characterized in that a print layer formed with the use of an ink containing, as its primary constituent, a polyamic acid mixed with a suitably selected coloring agent or the like is formed on a glass substrate. However, continued research subsequently performed has revealed that this method has the following problems. That is, it has been found that it has a problem or the like with respect to the uniformity and the dimensional precision of the thickness of a film printed for forming the color filter and, therefore, it is difficult to make the color filter comparable with or superior to that according to the conventional method in terms of the display quality. In other words, in the case with the printing process, and when it is viewed as a total color filter, an indentation between portions where the film thickness if great and small (hereinafter referred to as "indentation") tends to be formed. In the case where the indentation is great, no orientation treatment called rubbing can be effected uniformly over the entire surface of the substrate, and therefore, the display quality is adversely affected. Moreover, in the liquid crystal device of a type wherein a transparent electroconductive film is provided over the color filter, the indentation constitutes a cause of failure in electroconductivity and shortage in electroconductivity. Even if the electroconductivity is secured, in order to form a highly precise pattern, problems tend to occur at the time of masking during the subsequent patterning of the transparent electroconductive layer. In order to remove these problems, it can be contemplated to provide an overcoating layer on the surface thereby to improve the smoothness of the identation, but it is technically difficult and reduces the merits of the printing process which is low in cost.